Channel estimation errors impact on the sum rate maximisation in a JP‐CoMP transmission systems

Abstract

AbstractCooperation between multicell base stations (BSs) is a promising technique that has the potential to mitigate inter‐cell interference (ICI) and increase data rates without sacrificing additional frequency spectrum. Classical beamforming techniques have been used to eliminate the existing ICI and improve the sum rate of downlink cooperative multiple input multiple output transmission systems. However, a perfect knowledge of the channel state information at the transmitter is needed to perform adequate beamforming such as block diagonalisation or zero‐forcing preprocessing. In practice, this is not the case due to the presence of channel estimation errors.In this paper, we consider one particular scenario of the transmission coordination among multiple cell sites, namely the joint processing coordinated multipoint transmission scheme. A joint processing coordinated multipoint is composed of several BSs that cooperate to serve a set of mobile stations (MSs) and where both BSs and MSs are equipped with multiple antennas. In the context of this transmission scenario, we model the multicell cooperative system under the presence of channel estimation errors that are often neglected but that can significantly influence the obtained results. Furthermore, we consider a general framework where the distributed power from the BSs to the MSs is not constrained to be identical. We then propose a modified version of the classical block diagonalisation and zero‐forcing beamforming to efficiently mitigate the existing ICI. Finally, we evaluate the sum rate expression of the considered cooperative system, and we propose efficient alternatives to improve it without coupling the beamforming and the power control processes. Simulation results are given to support our claims. Copyright © 2013 John Wiley & Sons, Ltd.